The long-term objective of the asthma etiology project of the proposed Columbia Center for Children's Environmental Health (CCCEH) is to elucidate the role of exposures, before birth and up to age 2, to cockroach, dust mite and rodent allergens and to the environmental toxicants, respirable particulate matter (PM/2.5), diesel exhaust particulate (DEP) and environmental tobacco smoke (ETS), in allergen sensitization and recurrent wheezing. Allergen sensitization and recurrent wheezing have been found to be early predictors of asthma. Currently, little is known about the effects of prenatal and early postnatal environmental exposures on allergen sensitization and recurrent wheezing before age 2. Our study's hypotheses are that 1) the risks for allergen sensitization and recurrent wheezing before age 2 are increased be environmental exposures to cockroach, dust mite, and rodent allergens and to PM/2.5, DEP and ETS; 2) the adverse effect of allergen exposure on allergen sensitization and recurrent wheezing is increased by exposure to PM/2.5, DEP and/or ETS; and 3) To test the hypothesis that low plasma levels of antioxidant micronutrients (vitamins A, C, E) increase the infant's susceptibility to allergens, so that the adverse effects of allergens are greater for children with low levels of antioxidant micronutrients. The results of the Project will advance the knowledge about early-life risk factors for allergen sensitization and recurrent wheezing and the onset of asthma.